Currently there are the following methods for detecting the sole.
1. Moulding method: a mould of sole is made of parget or any other suitable plastic materials, by coating the materials over the sole. However, the mould lacks the digital data about the sole, and provides few information with low precision. The method can only be used for qualitative analysis and applications.
2. Scanning method: There are two scanning methods, i.e. scanning the sole without pressure thereon, and scanning the sole under pressure thereon. The former method is performed when the foot is hanging naturally, and the latter method is performed when the foot is stepping on a transparent glass. In both methods, the sole can be scanned by using the laser-scanning method, whereby the profile information of the sole can be obtained. However the measured information is a limited data because no pressure, or no fully pressure is applied on the sole. In addition, these methods are operated complicated with high cost, which were not often utilized.
3. Plane imaging method: 3D surface image with grid projection is obtained by CCD or other plane imaging methods, and the information of the 3D surface may be calculated based on the deformation of the grids. Although the method costs less and achieves an high resolution ratio of the sampled data, the deformation of the data may be too much, and the 3D gradient is limited by the angle of illumination to the grids. Thus the application of the method is also limited.
4. Inductance/capacitance method: when the planar materials are deformed, the inductance and/or capacitance thereon will vary, thus the curved surface can be measured by measuring the inductance and/or capacitance. However, the method has a low precision and a low antijamming ability, so that the method is unpractical.
5. Grating method: the surface to be detected is arranged as a grating matrix. During the detection, a displacement of 3D surface orthogonal to the grating matrix is recorded by the grating matrix, and thereby the information of 3D surface can be obtained. However, grating sensors usually have a big size, such that they might not be able to be arranged in a certain area, whereby the resolution ratio of the detection is reduced and the transmission mechanism is also complicated. The grating output is frequency signal, which requires a rapid response of the signal detection system in the grating matrix, as well as an excellent hardware/circuit. The method has a low resolution ratio and high cost.
6. Photoelectric reflex scanning method: the surface to be detected is arranged as a reflective phototube matrix. The phototubes receive reflected signals from detecting mechanism. The detecting mechanism is connected to the surface to be detected, such that the reflected signals vary upon the deformation of the curved surface. Although the method is easy and practical, there is no linear relationship between the reflected signals and the deformation/displacement, the dispersion between the components would be high such that it is difficult to achieve the standardization of the system.